D/A Section Overall Frequency Response - Motorola DSP56156 Manual

ON-CHIP CODEC FREQUENCY RESPONSE AND GAIN ANALYSIS
6.5.2.4

D/A Section Overall Frequency Response

Figure 6-12 and Figure 6-13 show the overall D/A section frequency response.
20
L
o
g
0
M
-20
a
g
n
-40
i
t
-60
u
d
e
-80
(
-100
d
B
)
-120
0.001
Figure 6-12 Log Magnitude Frequency Response of the
The frequency response of Figure 6-13(b) is not flat in the 0-4 KHz band. The interpolation
filter performed by the DSP core can compensate for this drop.
The D/A analog comb filter frequency response is flat in the audio band and does not need
any compensation (see Figure 6-10).
The digital second order D/A comb filter is the only filter that needs to be compensated.
6 - 26
20 40
D/A Section for F=2.048 MHz and D=128
DSP56156 ON-CHIP SIGMA/DELTA CODEC
60 80
Frequency (KHz)
Cascade of:
diff2-128.Filter
sum2-128.Filter
analogsum3-128.Filter
analogdiff3-128.Filter
analog-lp.Filter
100 128
MOTOROLA